math
posted by Terri on .
need to know how to solve this problem At what ratae will 150 double itself in 14 years?

First use the rule of 72 to get an approximation:
N=72/14= 5.1 %
The real calculation is:
(1+x)^{14} = 2
take log on both sides,
14log(1+x) = log(2)
log(1+x) = log(2)/14
1+x =e^{log(2)/14}
x = e^{log(2)/14} 1
=0.05076
The percentage required is 5.076%
(approx. equal to 5.1% estimated earlier)